| 1. |
- Ivanov, Sergey A., et al.
(författare)
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Spin and dipole order in geometrically frustrated mixed-valence manganite Pb3Mn7O15
- 2016
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Ingår i: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 27:12, s. 12562-12573
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Tidskriftsartikel (refereegranskat)abstract
- The structural, magnetic, and dielectric properties of Pb3Mn7O15 have been investigated using high-quality single crystals. Pb3Mn7O15 adopts a pseudo-hexagonal orthorhombic structure, with partially filled Kagom, layers connected by ribbons of edge-sharing MnO6 octahedra and intercalated Pb cations. There are 9 inequivalent sites in the structure for the Mn ions, which exist both as Mn3+ and Mn4+. Pb3Mn7O15 undergoes an antiferromagnetic transition below T-N similar to 67 K, with significant geometric frustration. Neutron powder diffraction on crushed single crystals allowed us to determine the low-temperature antiferromagnetic magnetic structure. We discuss the magnetic interaction pathways in the structure and possible interplay between the structural distortions imprinted by the lone-electron pair of Pb2+ cations and Mn3+/Mn4+ charge ordering.
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| 2. |
- Aidas, Kestutis, et al.
(författare)
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The Dalton quantum chemistry program system
- 2014
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Ingår i: WIREs Computational Molecular Science. - : Wiley. - 1759-0876 .- 1759-0884. ; 4:3, s. 269-284
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Tidskriftsartikel (refereegranskat)abstract
- Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, MOller-Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculated using these electronic-structure models. Molecular gradients and Hessians are available for geometry optimizations, molecular dynamics, and vibrational studies, whereas magnetic resonance and optical activity can be studied in a gauge-origin-invariant manner. Frequency-dependent molecular properties can be calculated using linear, quadratic, and cubic response theory. A large number of singlet and triplet perturbation operators are available for the study of one-, two-, and three-photon processes. Environmental effects may be included using various dielectric-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from for a number of UNIX platforms.
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| 3. |
- Tellgren, A., et al.
(författare)
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Myostatin rapid sequence evolution in ruminants predates domestication
- 2004
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 33:3, s. 782-790
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Tidskriftsartikel (refereegranskat)abstract
- Myostatin (GDF-8) is a negative regulator of skeletal muscle development. This gene has previously been implicated in the double muscling phenotype in mice and cattle. A systematic analysis of myostatin sequence evolution in ruminants was performed in a phylogenetic context. The myostatin coding sequence was determined from duiker (Sylvicapra grimmia caffra), eland (Taurotragus derbianus), gaur (Bos gaurus), ibex (Capra ibex), impala (Aepyceros melampus rednilis), pronghorn (Antilocapra americana), and tahr (Hemitragus jemlahicus). Analysis of nonsynonymous to synonymous nucleotide substitution rate ratios (K-a/K-s) indicates that positive selection may have been operating on this gene during the time of divergence of Bovinae and Antilopinae, starting from approximately 23 million years ago, a period that appears to account for most of the sequence difference between myostatin in these groups. These periods of positive selective pressure on myostatin may correlate with changes in skeletal muscle mass during the same period.
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| 4. |
- Tellgren-Roth, Asa, et al.
(författare)
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Keeping the blood flowing-plasminogen activator genes and feeding behavior in vampire bats
- 2009
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Ingår i: Die Naturwissenschaften. - : Springer Science and Business Media LLC. - 0028-1042 .- 1432-1904. ; 96:1, s. 39-47
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Tidskriftsartikel (refereegranskat)abstract
- The blood feeding vampire bats emerged from New World leaf-nosed bats that fed on fruit and insects. Plasminogen activator, a serine protease that regulates blood coagulation, is known to be expressed in the saliva of Desmodus rotundus (common vampire bat) and is thought to be a key enzyme for the emergence of blood feeding in vampire bats. To better understand the evolution of this biological function, we studied the plasminogen activator (PA) genes from all vampire bat species in light of their feeding transition to bird and subsequently mammalian blood. We include the rare species Diphylla ecaudata and Diaemus youngi, where plasminogen activator had not previously been studied and demonstrate that PA gene duplication observed in Desmodus is not essential to the vampire phenotype, but relates to the emergence of predominant mammalian blood feeding in this species. Plasminogen activator has evolved through gene duplication, domain loss, and sequence evolution leading to change in fibrin-specificity and susceptibility to plasminogen activator inhibitor-1. Before undertaking this study, only the four plasminogen activator isoforms from Desmodus were known. The evolution of vampire bat plasminogen activators can now be linked phylogenetically to the transition in feeding behavior among vampire bat species from bird to mammalian blood.
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| 5. |
- Ivanov, Sergey A., et al.
(författare)
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Chemical pressure effects on structural, dielectric and magnetic properties of solid solutions Mn3-xCoxTeO6
- 2014
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Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 50, s. 42-56
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Tidskriftsartikel (refereegranskat)abstract
- The effects of Co2+ doping on the structural, magnetic and dielectric properties of the multiferroic frustrated antiferromagnet Mn3TeO6 have been investigated. Ceramic samples of the solid solution series Mn3-xCoxTeO6 were prepared by a solid-state reaction route. X-ray and neutron powder diffraction and electron microscopy techniques were combined with calorimetric, dielectric and magnetic measurements to investigate the dependence of the crystal structure and physical properties on temperature and composition. It is shown that the compounds with x <= 2.4 adopt the trigonal corundum-related structure of pure Mn3TeO6 (space group 18) in the temperature range 5-295 K and that the lattice parameters a and c and the unit-cell volume V decrease linearly with increasing Co2+ concentration. The low-temperature magnetic susceptibility and heat capacity data evidence the antiferromagnetic ordering of all samples. The Neel temperature linearly increases with Co2+ concentration x. Curie-Weiss fits of the high temperature susceptibility indicate that the magnetic frustration decreases with x. The derived magnetic structure of Mn3TeO6 can be described as an incommensurately modulated magnetic spin state with k = [0, 0, k(z)] and an elliptical spin-spiral order of spins within the chains of MnO6 octahedra. With increasing Co2+ concentration the propagation vector kz changes from 0.453 (x = 0) to 0.516 (x = 2.4). The magnetic anisotropy changes as well, leading to a reorientation of the spiral-basal plane. A possible coexistence of long-range order of electrical dipoles and magnetic moments in Mn3-xCoxTeO6 is discussed.
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| 6. |
- Ivanov, Sergey A., et al.
(författare)
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Preparation, structural, dielectric and magnetic properties of LaFeO3-PbTiO3 solid solutions
- 2012
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Ingår i: Materials research bulletin. - : Elsevier BV. - 0025-5408 .- 1873-4227. ; 47:11, s. 3253-3268
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Tidskriftsartikel (refereegranskat)abstract
- Solid solutions of (1−x)LaFeO3–(x)PbTiO3 (0 < x < 1) have been prepared by conventional solid-state reaction. These complex perovskites have been studied by means of X-ray (XRPD) and neutron powder (NPD) diffraction, complemented with dielectric, magnetic, heat capacity and Mössbauer measurements. Complete solubility in the perovskite series was demonstrated. The NPD and XRPD patterns were successfully refined as orthorhombic (x ≤ 0.7) and tetragonal (x ≥ 0.8). A composition-driven phase transformation occurs within the interval 0.7 < x < 0.8. The samples with x < 0.5 showed evidence of long-range magnetic ordering with an G-type antiferromagnetic arrangement of the magnetic moments of the Fe3+ cations in the B-site with propagation vector k = (0,0,0). Based on the obtained experimental data, a combined structural and magnetic phase diagram has been constructed. The factors governing the structural, dielectric and magnetic properties of (1−x)LaFeO3–(x)PbTiO3 solid solutions are discussed, as well as their possible multiferroicity.
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| 7. |
- Ivanov, Sergey A., et al.
(författare)
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Spin and Dipole Ordering in Ni2InSbO6 and Ni2ScSbO6 with Corundum-Related Structure
- 2013
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 25:6, s. 935-945
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Tidskriftsartikel (refereegranskat)abstract
- The complex metal oxides Ni2InSbO6 (NISO) and Ni2ScSbO6 (NSSO) have been prepared in the form of polycrystalline powders by a solid state reaction route. The crystal structure and magnetic properties of the compounds were investigated using a combination of X-ray and neutron powder diffraction, electron microscopy, calorimetric, and magnetic measurements. The compounds adopt a trigonal structure, space group R3, of the corundum related Ni3TeO6 (NTO) type. Only one of the octahedral Ni positions (Ni(2)) of the NTO structure was found to be occupied by In (Sc). NTO has noncentrosymmetric structure and is ferroelectric below 1000 K; dielectric and second harmonic measurements suggest that also NISO and NSSO are correspondingly ferroelectric. Magnetization measurements signified antiferromagnetic ordering below T-N = 60 K (NSSO) and 76 K (NISO). The magnetic structure is formed by two antiferromagnetically coupled incommensurate helices with the spiral axis along the b-axis and propagation vector k = [0, k(y),0] with k(y) = 0.036(1) (NSSO) and k(y) = 0.029(1) (NISO). The observed structural and magnetic properties of NISO and NSSO are discussed and compared with those of NTO.
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| 8. |
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| 9. |
- Tellgren, Roland, 1930-, et al.
(författare)
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Substitution mechanism and structural study of Ag-doped LiCu2O2
- 2017
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Ingår i: Solid State Sciences. - : ELSEVIER SCIENCE BV. - 1293-2558 .- 1873-3085. ; 70, s. 36-40
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Tidskriftsartikel (refereegranskat)abstract
- Plate-like stoichiometric crystals of Ag-doped LiCu2O2 have been grown by slowly cooling Li2CO3 center dot 4(1 - x)CuO center dot 4xAgNO(3) (0 <= x <= 0.5) melts. X-ray single crystal diffraction has shown that the crystals are isostructural with LiCu2O2 and contain around 5 at % Ag (relative to the Cu atoms). The addition of silver to lithium cuprate crystals significantly increases their electrical conductivity but has little effect on the temperature behavior of their magnetic moment. The possible substitution mechanism is determined which supports Ag+ <-> Cu+, rather than Ag+ <-> Li+ in the Ag-doped LiCu2O2 crystals.
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| 10. |
- Tellgren-Roth, C., et al.
(författare)
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Complete Genome Sequence and Methylome of the Type Strain of Shewanella algae
- 2021
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Ingår i: Microbiology Resource Announcements. - : American Society for Microbiology. - 2576-098X. ; 10:31
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Tidskriftsartikel (refereegranskat)abstract
- We report the complete genome sequence and base modification analysis of the Shewanella algae type strain CECT 5071 (= OK-1 = ATCC 51192 = DSM 9167 = IAM 14159). The genome is composed of a single chromosome of 4,924,764 bp, with a GC content of 53.10%.
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